This invention relates to a gasket material, and more particularly, to an automotive gasket of a paper base material bearing a coating of a silicone material.
A gasket is a deformable layer of packing material that is designed to be firmly held between at least two contact surfaces having a joint intended to be sealed with the gasket in order to prevent leakage from the joint. The basic function of a gasket is to fill the space between two imperfect faces sought to be joined in a fluid tight relationship. The use of a gasket eliminates the need for costly finishing of the faces which would otherwise be necessitated. Gaskets are manufactured in many varied shapes and sizes but in general are flat thin materials which can be compressed. They can be constructed of matural or synthetic rubber, felt, cork, vegetable fiber, paper, asbestos, plastic, and soft metallic materials such as lead and copper. The gasket may be employed in service in duties ranging from the prevention of leakage of liquids, to the rendering of certain joints to be gas tight such as high temperature engine exhaust manifolds. The ideal gasket is a resilient predictably compressible composition of one or more materials which conforms easily to joint surface irregularities, and which can compensate for joint distortion during operation and thermal fluctuations.
For most applications, the gasket material alone is not sufficient to form a seal due to the many voids and channels that exist in the material. It has therefore become common practice to incorporate additives and impregnants into the gasket material such as fillers, binders, sealants, and saturants, of varied and complex description, in an attempt to compensate for these voids and channels, thereby rendering the gasket material to be more leak proof.
For example, representative of additives and impregnants which have been used in the past are glue, grease, wax, rubber such as styrene-butadiene, plastics, phenolic resins, elastomers such as chloroprene, nitriles, and fluoroelastomers, and silicones. Thus, in U.S. Pat. No. 2,956,908, issued Oct. 18, 1960, there is described a gasket matrial specific to automotive vehicle application and wherein there is included as a coating thereon a mixture of a silicone fluid and castor oil. A mixture of chrysotile asbestos and a heat curable siloxane elastomer is taught in U.S. Pat. No. 3,453,228, issued July 1, 1969, although the use of such material as a gasket is not specifically disclosed. However, a cylinder head gasket including a silicone rubber binder is shown in U.S. Pat. No. 4,355,068, issued Oct. 19, 1981.
Thus, it should be apparent that the use of silicone materials in gaskets is not new. What is new, however, and covered by the present invention, is a coating for a gasket material having improved water resistance.